1. Field of the Invention
The present invention relates to a semiconductor device, and more particularly to a semiconductor device which includes an input signal discrimination unit that can cope with a change in operating voltage.
2. Description of Related Art
Small amplitude signals are input to semiconductor devices such as a DRAM (Dynamic Random Access Memory). Such input signals are compared with a reference potential by an input signal discrimination unit, and their logic levels are discriminated basedon the comparison results.
The input signal discrimination unit needs a high sensitivity in order to discriminate a minute potential difference between an input signal and the reference potential. Among the known input signal discrimination units having a high sensitivity are the ones described in Japanese Patent Application Laid-Open No. 2000-357961.
When the input signal discrimination unit changes in operating voltage, its sensitivity also varies. More specifically, when the operating voltage of the input signal discrimination unit drops, the source-drain currents (operating currents) of the transistors therein decrease to reduce the sensitivity of the input signal discrimination unit.